The ability to imagine things that do not exist has long been considered uniquely human. Young children naturally engage in pretend play, hosting tea parties with dolls and creating imaginary friends. Scientists have observed hints of similar behavior in wild apes—young female chimpanzees carrying sticks like mothers cradle infants, or captive chimps seemingly dragging invisible blocks—but no one had tested whether apes could truly pretend in controlled conditions.
Dr. Christopher Krupenye and Dr. Amalia Bastos, researchers from Johns Hopkins University and the University of St. Andrews, designed experiments modeled after childhood development tests from the 1980s. Their subject was Kanzi, a bonobo whose name means treasure in Swahili, known for his language comprehension and ability to respond by pointing.
In three experiments conducted at the Ape Initiative in Des Moines, Iowa, Kanzi participated in make-believe scenarios. Researchers set out transparent cups and an empty pitcher, then pretended to pour juice into both cups before pouring one back into the pitcher. When asked where the juice was, Kanzi pointed to the correct cup 34 out of 50 times. To confirm he understood the juice was imaginary, researchers presented him with both real and pretend juice, and Kanzi chose the real option 14 out of 18 times. A third experiment with imaginary grapes yielded similar results.
The findings, published in the journal Science, suggest the capacity to understand pretend objects exists within the cognitive potential of enculturated apes and likely emerged six to nine million years ago in our common evolutionary ancestors. Krupenye noted this challenges assumptions about animal cognition, explaining that if roots of imagination are shared with apes, people should question whether other animals are simply living constrained to the present moment.
The research team plans to explore whether other apes and animals can engage in pretend play, and to investigate additional facets of imagination such as thinking about the future or understanding what others are thinking. Kanzi, who died in 2025 at age 44, leaves behind a legacy that fundamentally changes how we understand the mental lives of our closest relatives.